on the inside. The combination of the three layers, along with different colours, different styles and so on, gives 6,000 product varieties.
It would be impossible to do that [inspect] manually for that amount of products within a reasonable time,’ commented Mark Shelton, managing director of Shelton Vision ‘The high turnover and wide range of products is typical of textiles.’
Each variety of laminated fabric was trained on Shelton Vision’s inspection system. The company developed a way of automating the training of its vision software, so that the first time the system sees a new product it realises that the fabric is not in its database and will initiate automated training.
Machine vision holds a lot of promise for quality assurance in textile production if system builders can overcome the hurdles involved in inspection, for which product variation is only one.
The first place where a vision system might be used is on the machine on which the fabric is formed, so a loom or a knitting machine. ‘There might be 200 to 400 looms, or more, in a factory, so to put a vision system on each of those is restrictive, in terms of cost,’ commented Shelton. ‘You need very low hardware costs in order to do this, although things are moving in that direction and it’s something Shelton Vision is actively working on, and has delivered a number of systems.’
Image acquisition from a camera installed on a loom though is difficult, according to Olivier Despont, business development at Swiss vision software firm Vidi Systems, because of the vibrations from the machine. Vidi Systems is in discussion with companies for field deployment of its image analysis software in textile inspection, including a couple of machine builders for inspecting on the loom, although Despont said this will more likely be a long-term project because there first needs to be a camera system that deals with vibration. Vidi Systems has carried out feasibility tests for inspecting narrow fabrics, such as harnesses and security belts.
The alternative to installing cameras on the loom is to have a standalone inspection unit, a more common option. In weaving in particular, it’s possible to mend defects, so the raw fabric could potentially be run through a high-speed inspection system offline, to decide which defects are worth repairing. According to Shelton, in general, 90 per cent of the value of the fabric is the raw material.
Once the fabric is formed it is then dyed, finished, heat set, or coated before it’s used for its final purpose. ‘Each of those processes adds value, so it’s worth inspecting either during the process if you can stop the machine once a defect is detected, or before the fabric goes into the next process stage, so value is not added to something that’s already defective,’ explained Shelton.
Source : www.imveurope.com